The present invention relates to a spot welding control system and a spot welding control method for a high quality spot welding to be achieved by detecting time-dependent variations of inter-electrode displacement amount while welding.
A sureness or state of a spot welding is inspected by examining an attribute of a thermal expansion of a welding object during conduction of welding current or along a growth of a nugget: by a maximum displacement in Japanese Patent P48-41422 and Japanese Patent P53-4057, by a displacement rate in U.S. Pat. No. 3,400,242 and Japanese Patent P53-4057, and by a contracting state in Japanese Patent Application Laid-Open Publication No. 7-232279.